The present invention relates to a process for fluorinating polymers to form low energy fluorinated polyolefin surfaces an to the fluorinated polymers so-produced.
Prior to the present invention, attempts have been made to fluorinate polyolefins such as polyethylene and polypropylene to form low energy surfaces of the type that characterize the Teflon-type polymers. These prior attempts have utilized fluorine gas generally at relatively high concentrations and in the substantial absence of species such as oxygen which compete with fluorine for the reactive sites on the polyolefin surface. Unfortunately, when utilizing fluorine under relatively mild conditions of temperature, pressure and fluorine concentration wherein polymer degradation is insubstantial, the reaction time to effect fluorination is relatively large; the resultant surface does not have the low energy desired due to the presence of oxygen thereon, as shown by Clark et al., Journal of Polymer Science; Polymer Chemistry Edition, Volume 13, pages 857-890 (1975). The products of prior fluorination procedures utilizing fluorine gas include a number of species containing only partial fluorine substitution of hydrogen. This also is undesirable since the presence of hydrogen tends to increase the free energy of the polymer surface.
Accordingly, it would be highly desirable to provide a means for substantially completely fluorinating a polymer in order to form a low energy surface. It would be desirable to provide such a means wherein the polymer substrate is not substantially degraded during fluorination. Furthermore, it would be desirable to provide such a means wherein the product contains substantially no oxygen bound thereto.